1. Field of the Invention
The present invention relates to a solid-state image sensing apparatus, and a package of the solid-state image sensing apparatus, and in particular, to a solid-state image sensing apparatus suitable for use in a linear sensor, and a package of the solid-state image sensing apparatus.
2. Description of Related Art
For a solid-state image sensing apparatus in electronic equipment such as a copy machine, scanner, fax machine, and so forth, for reading images and character information, a one-dimensional solid-state image sensing chip made up by arranging photodiodes in a line, the so-called linear sensor, has been in wide spread use. Much use has been made of, for example, a CCD (Charge-Coupled Device) linear sensor, and a CMOS (Complementary Metal-Oxide Semiconductor) linear sensor Those solid-state image sensing apparatuses are attached to a printed circuit board to be then mounted on the electronic equipment. There are cases where an optical apparatus (reducing glass) for image reduction, together with the solid-state image sensing apparatus, is attached to the printed circuit board.
In order to accurately read information on images and so forth, the electronic equipment is optically adjusted with precision before assembling. However, when the electronic equipment is in operation, heat evolution occurs therein, so that the so-called warpage (the printed circuit board is distorted or kinked by the agency of heat) occurs to the printed circuit board with the solid-state image sensing apparatus attached thereto. As a result, warpage occurs to the solid-state image sensing apparatus as well, thereby causing an optical distance between the photodiodes of the solid-state image sensing apparatus to undergo displacement, so that a subject for image-sensing will be out of focus, resulting in deterioration in picture quality. As occurrence of the heat evolution has since become more pronounced due to recent increase in read rate, so more serious has become a problem of the warpage occurring to the solid-state image sensing apparatus.
In JP-A No. 2007-281451 (hereinafter referred to as a first prior art), there has been described a solid-state image sensing apparatus wherein a shape of each of outer leads is devised such that a deforming stress applied to a printed circuit board is absorbed by the outer leads, thereby mitigating a stress applicable to a solid-state image sensing chip. There will be described hereinafter a solid-state image sensing apparatus 10 as set forth in the first prior art with reference to the accompanying drawings.
FIG. 1 is a perspective view of the solid-state image sensing apparatus 10, FIG. 2 a sectional view taken on line II-II, in FIG. 1, FIG. 3A is a plan view of a lead frame 2 used in the solid-state image sensing apparatus 10, and FIG. 3B is a detailed plan view of outer leads 2b1.
The solid-state image sensing apparatus 10, shown in FIG. 1, comprises a package body 1 made of a synthetic resin, having long sides and short sides, a solid-state image sensing chip 3 encased in a recess formed in the package body 1, and a plurality of the outer leads 2b1, disposed so as to be arranged on a side face of the package body 1, in the direction of the long side thereof. A plurality of the outer leads 2b1 are similarly disposed on the opposite side face of the package body 1, thereby making up the so-called DIP (Dual Inline Package) structure. A transparent sheet 4 excellent in light transmittance is mounted on the top surface of the package body 1, thereby sealing the recess, and the solid-state image sensing chip 3. The solid-state image sensing apparatus 10 is connected to a printed circuit board 20. Each of the plurality of the outer leads 2b1 has a bend portion 2b10.
As shown in FIG. 2, the outer lead 2b1 each are linear as seen from the direction of the short side of the package body 1 (in the x-direction in FIG. 1) The solid-state image sensing chip 3 is mounted so as to be in the pattern of an island to be electrically continuous with inner leads 2b2, respectively, by a bonding wire 5.
FIG. 3A is the plan view of the lead frame 2 used in the solid-state image sensing apparatus 10, and FIG. 3B is the detailed plan view of the outer lead portion 2b1. The bent portion 2b10 is in a shape resembling the letter S, comprising a bend 2b11 arc-like in shape, and a bend 2b12 arc-like in shape, disposed on the right side, and the left side of the center line Z0 of the outer lead portion 2b1 respectively. When the printed circuit board is expanded in the direction parallel with the long side of the package body 1 (in the x direction) due heat evolution, an end portion A of the outer lead 2b1 fixed to the printed circuit board is caused to move in the x direction. A force pulling the bent portion 2b10 directly below via the end portion A will act on the bent portion 2b10, however, because the bend 2b11 and the bend 2b12 are deformed, a stress exerted on the package body 1 via a root 2b13 of the outer lead 2b1 is controlled. As a result, a warpage amount of the solid-state image sensing chip 3 can be controlled to a small value.
Besides the above-described, a semiconductor device, and an electronic component, wherein a bent portion is provided halfway through each of outer leads, thereby absorbing a stress, have been disclosed in JP-A No. 9(1997)-246452 (hereinafter referred to as a second prior art), JP-A No. 11(1999)-307708 (hereinafter referred to as a third prior art), and JP-A No. 6(1994)-45724 (hereinafter referred to as a fourth prior art), respectively.
The inventor, however, has since realized that those prior arts each have the following problem.
With the solid-state image sensing apparatus 10 according to the first prior art, if a pitch between the outer leads 2b1 adjacent to each other becomes narrow, the bent portion 2b10 should be rendered smaller in width in order to prevent the outer leads 2b1 from coming into contact (being shorted) with each other. More specifically, the bend 2b11 and the bend 2b12 are reduced in size, so that an effect of controlling the stress exerted on the package body 1 will be decreased.
In contrast, in the case of the second to the fourth prior arts, respectively, respective bends are shown in as bent-state when seen from a direction in which respective outer leads protrude toward respective side faces of a package body (in the same direction as in FIG. 2), and it is presumed that the respective outer leads are shown linear as seen in a direction in which the respective outer leads are rotated through 90 degrees sideways (in the Y direction in FIG. 1). Accordingly, with the second to the fourth prior arts, respectively, even if respective bends are increased in size, it seems that there is no risk of the outer leads adjacent to each other coming into contact with each other.
However, the second and third prior arts each are not suited for application to a slender solid-state image sensing apparatus such as the linear sensor because the outer leads are of a surface-mounting type. That is, the outer leads simply bonded to the surface of a printed circuit board is unable to fully absorb a stress applied on the slender solid-state image sensing apparatus, so that the outer leads will be exfoliated.
Meanwhile, in the fourth prior art, there is disclosed a mount-structure of a component, wherein a lead is inserted into a hole formed in a printed circuit board to be soldered thereto. As shown in FIG. 4, a lead 42 of a component 41 is provided with elasticity by bending the same, and an end portion 47 of the lead 42 is inserted into a hole of a printed circuit board 44. A bend portion 43 is butted against an upper region around the hole, and the end portion 47 of the lead 42 is bonded to a pattern 45 of the printed circuit board 44 with the use of a solder 46.
The bend portion 43 serves as a stopper for preventing the lead 42 from being further inserted into the hole of the printed circuit board 44. That is, the bend portion 43 is formed in order to keep the component 41 out of contact with the printed circuit board 44. If the component 41 is the solid-state image sensing apparatus, variation and distortion in the shape of the bend portion 43 will cause the solid-state image sensing apparatus to be tilted, so that a subject for image-sensing will be out of focus, thereby deteriorating picture quality.